1. Field of the Invention
The present invention relates to a driving circuit and an organic light emitting display including the driving circuit, more particular to a driving circuit, which may reduce errors in realizing gray levels by preventing a voltage drop occurring in an analog switch in order to improve the linearity, and an organic light emitting display including the driving circuit.
2. Description of the Related Art
In a flat panel display device, a plurality of pixels are formed on a substrate and forms a display region. A scan line and a data line are coupled to each of the pixels, and an image is displayed by applying driving signals to the pixels.
Flat panel display is classified into an active matrix type luminescence display and a passive matrix type luminescence display according to its driving method. These types of flat panel displays have been used for display devices of portable information terminals such as a personal computer, a portable telephone, and a personal digital assistant (PDA), and monitors of all kinds of information devices. A liquid crystal display (LCD) including a liquid crystal panel, an organic light emitting display including an organic light emitting diode, and a plasma display panel (PDP) including a plasma panel are examples of flat panel displays. Recently, various flat plate displays capable of reducing weight and volume have been developed overcoming the disadvantages of bulky cathode ray tubes (CRT).
FIG. 2 is a circuitry diagram showing a resistor unit for generating various voltage levels in a D/A converter, which can be used in a data driver of an organic light emitting display. Specifically, FIG. 2 shows a resistor unit for generating eight voltage levels. In order to generate eight voltage levels, eight resistors are serially coupled to each other. A first reference voltage having a higher voltage and a second reference voltage having a lower voltage are applied across the resistors. The difference of the first reference voltage and the second reference voltage are divided by the 8 resistors to obtain divided voltages, which are data voltages.
The D/A converter shown in FIG. 2 generates 8 data voltage levels, which are divided by the 8 resistors. Since the number of the data voltage levels is fixed, the number of gray levels to be generated is also fixed. Therefore, in order to generate another gray levels such as 256 gray levels, 128 gray levels, and 64 gray levels, the D/A converter should have another circuit design that is different from the circuit shown in FIG. 2. Because the data driver includes an unique resistor unit for achieving a specific gray levels, the data driver should be replaced in order to realize another gray levels, which causes inconvenience and reduces flexibility.